1. Field of Invention
The invention relates to wearable transmitter assemblies for monitoring individuals and more specifically to such an assembly secured with a strap to an appendage of the individual. The invention has particular utility with transmitters in "house arrest" systems including tamper detection features coupled through the strap.
2. Description of the Prior Art
Personal monitoring systems are known to include a wearable transmitter, sometimes called a tag or beacon, that communicates with a field station linked to a monitoring center. In house arrest systems, for example, the presence or absence of an individual is monitored to determine when the individual leaves and returns to a predetermined location, frequently a home. A transmitter on the individual broadcasts a radio frequency signal at relatively low power. A corresponding field station in the home includes a receiver for detecting the signal whenever the transmitter is within range. If the monitored individual leaves the home, the distance from the transmitter to the field station exceeds the range of the system and it loses the signal. Unscheduled signal losses initiate a reporting sequence including notification of an infraction sent to the monitoring center.
The transmitter usually is secured with a strap selected to fit comfortably but snugly around a wrist or ankle of the individual so the transmitter cannot be removed. Tamper circuits in the transmitter housing detect any cutting or removal of the strap that might be associated with unauthorized removal of the transmitter. Tamper information is transmitted to the home receiver and forwarded to the monitoring center. If the transmitter is not within range of the system when the tamper occurs, the tamper signal is stored and transmitted later when communication with the system is reestablished.